In the railway rolling stock arts it is well known to provide a railway truck to support a car body with respect to the track by means of a plurality of wheelsets which are disposed in rolling engagement on the railway track. For example, the well known three piece truck commonly employed in freight haulage service includes a pair of laterally spaced, elongated side frames which are supported adjacent their longitudinal ends by a pair of bearing adapters supported on roller bearing assemblies carried by respective wheelset axle ends. A bolster extends transversely between the side frames and its ends are supported in the side frame transom windows by load spring groups to thereby provide sprung support for the bolster and the car body, which is supported on a center plate bearing portion of the bolster.
In a conventional three piece freight car truck, the two longitudinally spaced wheelsets are kinematically constrained by their connecting side frames to run in an approximately parallel fashion, although sustained lateral wheelset oscillations can occur. This well-known phenomenon, often referred to as hunting, is characterized by relative lateral shear and in-phase yaw between the wheelset axles. To prevent hunting, low operating speed limits often must be observed.
Constraint of the wheelset axles by the side frames in a substantially parallel relation also inhibits the movement of the wheelsets to a radial position while negotiating track curves. This results in a non-zero angle of attack for the axle. The wheelset is therefore guided through the track curve by flange-to-rail contact, thereby increasing both rolling resistance and wear.
Practitioners in the art have continually sought improved structures for enhanced inter-axle constraint of railway truck wheelsets to limit inter-axle shear and to implement truck steering through coordinated, mutually opposed wheelset yaw movements.
The prior art includes numerous examples of railway truck wheelset inter-engagement schemes. The following issued patents are representative: U.S. Pat. Nos. 4,131,069, 4,729,324, 4,781,124, 4,889,054, 4,628,824, 4,244,297, 4,841,873, 325,532, 555,857, 1,105,291, 4,676,172, 1,493,682, 4,300,454, 4,480,533 and 4,258,629.